The simplest form of fly trap consists of a support structure with at least one surface having an adhesive coating. When flies come in contact with the adhesive coating, they stick. An example of such a fly trap is U.K. Patent Application 2,058,537 which was published Apr. 15, 1981. This reference discloses a elongate sheet with suitable adhesive on one face. The elongate sheet is intended to be hung in a room infested with flies. When a fly comes in contact with the adhesive it is held securely to the elongate sheet. The elongate sheet has a transverse hinge which enables the fly trap to be alternately configured or moved to a closed position.
The key to the effectiveness of fly traps, such as the U.K. Patent is the extent to which flies are prone to come in contact with the adhesive.